Wednesday, April 30, 2014

Lingering Concerns about Cold Injury in Corn



As a general rule, corn can sustain more injury (such as cold) because it’s growing point remains protected safely under the ground until around the V5 growing stage.  Because of this, corn is more likely to recover from damage with little damage.   

Cold Injury of Corn
However, there are always those exceptions and with corn this exception to the general rule can occur if corn sustains a lethal temperature of below 28 degrees for a few hours.  If this occurs, the corn growing point can die, even if the corn plant is younger than V5 and the growing point remains below ground.   You can cut the plant open and examine to the growing point to see if it appears brown; however, unfortunately, the only way you will really know if you have corn loss due to corn injury is if you wait a few days for signs of recovery.   

A corn seedling (in a less than desirable seedbed) showing stress due to cool temperatures; however later recovered later in the season.



Cold Imbibitional Chilling Damage of Corn
There are many theories as to what causes cold imbibitional chilling damage, but one of the main theories is that injury occurs to the germinating corn seedling when there are soil temperatures swings that mesocotyl growth.  When a corn seed first germinates, the seed absorbs 30 percent of its weight in water and thus, the radical or (first root) emerges.  Typically at this stage of the germination game, soil temperature swings have no affect on growth and as a review, emerged seedlings are relatively resistant to cold.  You could have problems with seedling growth if soil temperatures fluctuate during mesocotyl growth, which in turn can cause the newly emerging seedling to have stunted growth and distorted leaves.  The following University of Nebraska - Lincoln article addresses more details on Cold Imbibitional Chilling Damage of Corn 



Suspected Cold Imbibtional Chilling Damage of Corn

Also keep in mind, once the corn plant has sustained cold stress, it becomes much too susceptible to disease, pests, and even herbicide injury.  Stand counts will need to be taken to determine if replanting should occur. 


Scouting for corn emergence problems is strongly encouraged early in the season so that prompt replant decisions can be made.  Burrus provides an easy to use replant chart in their 2014 Growing “pocket” Guide on page 18.   This replant chart can also be found at the Burrus website, (www.burrusseed.com), by choosing the Resources tab, then clicking on Reference Materials, and  clicking on “Should I replant my corn?"

Sunday, April 27, 2014

Evaluate Corn Stands Early

It seems logical, but corn stands should be evaluated early in the season.  When I say early, I mean a week or two after emergence (VE to V3) and if needed, replanting can occur.   However, this sometimes is easier said than done, depending on the weather and how busy planting season has progressed.  At growth stages VE to V3, the corn plants main root system is the mesocotyl.   Unfortunately, growers often realize a stand, when it is too late to replant.  At the growth stage V3 to V4, the corn plant’s nodal roots become the plants primary source of water and nutrients. 

Did you know there was an app for that? (To help with corn growth stages and production decisions.)
The University of Kentucky Extension just released a Corn and Soybean Production App.
Picture taken from http://about.extension.org/2013/06/03/extension-kentucky-launch-corn-soybean-app/

The corn and soybean app was designed to help growers plan their work in the office or on the field. The app includes a crop calendar for corn and soybeans, some of the growth stages for corn, access to crop progress reports and useful facts for helping make production decisions.”  For more information, about the Corn and Soybean Production App, you can check out the following blog called, eXtension, Kentucky Launch Corn and Soybean App.

When it comes to reduced corn emergence or uneven stands, often times, it is easy to put the blame on root rot diseases, insects, herbicide injury, and even nematodes. The underlying theme is that pest, disease, and herbicide injury issues are often a problem if corn lacks vigor.  Even though pests and diseases get a lot of attention, more attention should be on environmental as well as seedbed conditions at planting.  Poor weather and seedbed conditions can cause stress to plants and lead to disease and pest issues.  

There can be various factors that can restrict this root growth.  In previous blogs we have talked about how low soil temperature (below 50 degrees F.) can limit corn growth, as well as other factors such as soil moisture at planting, soil surface crusting, soil to seed contact, soil compaction, or a mixture of these factors that can limit either the root or corn plant’s ability to properly grow for optimum performance.